Synonyms: incredible, unbelievable
Definition: beyond belief or understanding
Usage: at incredible speed; the book's plot is simply incredible
Similar words: astounding, dumbfounding, dumfounding
Definition: bewildering or striking dumb with wonder
Similar words: fabulous
Definition: barely credible
Usage: the fabulous endurance of a marathon runner
Similar words: tall, marvellous, marvelous, improbable
Definition: too improbable to admit of belief
Usage: a tall story
Similar words: undreamed, undreamed of, undreamt, undreamt of, unimagined
Definition: not imagined even in a dream
Synonyms: improbable, unbelievable, unconvincing, unlikely
Definition: having a probability too low to inspire belief
Similar words: implausible
Definition: having a quality that provokes disbelief
Usage: gave the teacher an implausible excuse